NDFF Butterfly monitoring program

The aim of the NEM butterfly monitoring program is to collect up-to-date information about changes to the butterfly population in the Netherlands. Standardised survey methods and locations are used to find possible causes of changes. Routes are marked across the country so that observers can all use the same counting method. Records are kept every week during the season on what butterfly species occur in a location and how many. The people in the field provide basic information. Dataset available via https://www.ndff.nl/english / [e-mail] Positive observations without zeros. 1,945,346 records (March 2018) NDFF protocol 3.201 https://www.ndff.nl/overdendff/validatie/protocollen/3-201-landelijk-meetnet-vlinders/